The present invention relates to an apparatus and method for detecting the condition of an item and, particularly, but not exclusively, to an apparatus and method for detecting a specific condition of a motor vehicle tire.
It is well known for the poor condition of items such as motor vehicle brake pads to be detected by appropriate electrical means. Typically, excessive brake pad wear is indicated by the closing of a simple circuit. When the brake pads are worn to a predetermined level, a pair of spaced apart wires embedded in one or more of the pads becomes exposed. During operation of the braking system, the exposed wires are pressed against a metal brake disc and, as a result, an electric circuit is closed. Suitable means for warning the motor vehicle driver is then activated.
Although the aforementioned means for detecting a particular condition of an item is adequate for many applications, it cannot be conveniently adapted to circumstances where connection of the item in question to an electric circuit is problematic. This may be the case where the item is required to rotate at high angular velocities, for example, a motor vehicle tire.
Due to the harsh conditions in which motor vehicle tires operate, it has not been possible in the past to provide a vehicle with means for conveniently, reliably and inexpensively detecting a particular level of tire wear. Since no automatic means for indicating excessive tire wear has been available for motor vehicles, the inadvertent and highly dangerous use of over worn tires has traditionally only been avoided through frequent visual inspection of the tread on each motor vehicle tire. However, inspections of this type are time consuming and inconvenient, and they are generally not adequately completed by motor vehicle users, particularly the users of privately owned motor vehicles. As a result, many motor vehicles are driven in a dangerous condition without the knowledge of the driver.
It is an object of the present invention to provide apparatus for detecting a specific condition of an item, particularly an item located in a remote environment or exposed to harsh conditions (for example, the tire of a motor vehicle).
It is also an object of the present invention to provide apparatus for detecting a specific condition of an item in a convenient, reliable and inexpensive manner.
It is a further object of the present invention to provide detecting apparatus which does not require maintenance.
An object of the present invention is also to provide a method for detecting a specific condition of an item, particularly an item located in a remote environment or exposed to harsh conditions (for example, the tire of a motor vehicle).
Furthermore, it is an object of the present invention to provide a method for detecting a specific condition of an item in a convenient, reliable and inexpensive manner.
A first aspect of the present invention provides apparatus for detecting a specific condition of an item, the apparatus comprising: a structure for radiating radio frequency energy in response to the reception by said structure of radio frequency energy; said structure having a first configuration which in use, is changed to a second configuration in response to said item attaining said specific condition; said change in configuration producing a detectable difference in radio frequency energy radiated from said structure.
A specific level of tire wear may be detected through appropriate use of apparatus according to the present invention. For example, the structure for radiating radio frequency energy may be embedded in the rubber tread of a tire during the tire manufacturing process. The depth of tread at which the structure is located will determine the level of tire wear permitted before detection occurs. Once the tire tread has worn sufficiently for said structure of the present invention to become exposed, further use and consequential wear of the tire will cause said structure to repeatedly strike a road surface and itself become worm. Accordingly, said structure may be changed from a first configuration to a second configuration as a specific tire condition (for example, excessive wear) is attained. In consequence of the change in configuration of said structure, the characteristic response of said structure to the reception of radio frequency energy is also changed. Thus, whether or not a tire provided with apparatus according to the present invention suffers from excessive wear may be determined by periodically illuminating said tire with radio frequency energy and monitoring the radio frequency energy radiated in response thereto from said structure embedded in the tire tread.
Preferably, said structure comprises a member adapted to be ablated during use when said item attains said specific condition. It is further preferable for said structure to comprise two spaced members which are connected to one another by said member adapted to be ablated. Said structure may comprise a plurality of members adapted to be ablated during use. It is particularly desirable for at least one member of the said plurality of members to be adapted to be ablated during use when said item attains a condition different to that attained when another member of said plurality of members is ablate during use. Said structure may be a unitary component.
Furthermore, it is preferable said structure to comprise two elongate elements, first ends of the elements being connected to one another and second ends of the elements being connected to one another, each element comprising two spaced members which are connected to another by a member adapted to be ablated. A member may be adapted to be ablated by virtue of said member projecting from the remainder of said structure. Alternatively, a member may be adapted to be ablated by virtue of said member being of a material different to that of the remainder of said structure. The member adapted to be ablated may be a bi-metallic strip.
Preferably, said structure incorporates at least one elongate slot. It is further preferable for said structure to be of an elongate shape. In the first configuration, said structure ideally comprises one or more bridge elements extending from one side of the at least one slot to the other side thereof. Each bridge element preferably protrudes so as to leave vacant the space defining the slot. A bridge element or member adapted to be ablated may be a bi-metallic strip. One side of the at least one slot may be connected to the other side thereof by means of a linear or non-linear mixer.
A second aspect of the present invention provides a method for detecting a specific condition of an item, the method comprising the steps of: providing said item with the apparatus defined hereinabove for detecting a specific item condition; transmitting radio frequency energy to said apparatus and receiving radio frequency energy radiated therefrom; and monitoring for radiated radio frequency energy corresponding to the attaining of said specific condition
Thus, the apparatus and method of the present invention have the advantage over the prior art of allowing the automatic detection of a specific item condition even where the item in question is located in a remote environment or exposed to harsh conditions. The apparatus of the present invention functions in a simple and passive manner. Accordingly, said apparatus is inexpensive to manufacture and can be conveniently integrated within an item to be monitored. The simple operation of said apparatus results in a high degree of reliability.
Furthermore, since the apparatus of the present invention operates in a passive mode, said apparatus does not require maintenance. Unlike other sensing means, the apparatus of the present invention does not require batteries to be installed and periodically replaced.